After Arkansas storm deaths we ask: How bad can a tornado get?

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Photos:Photos: 10 deadliest U.S. tornadoes

10 deadliest U.S. tornadoes – 1.The "Tri-State Tornado," which killed 695 people and injured 2,027, was the deadliest tornado in U.S. history, according to the National Oceanic and Atmospheric Administration. The tornado traveled more than 300 miles through Missouri, Illinois and Indiana on March 18, 1925, and was rated an F5, the most powerful under old Fujita scale (winds of 260-plus mph).

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Photos:Photos: 10 deadliest U.S. tornadoes

10 deadliest U.S. tornadoes – 2. The "Natchez Tornado" killed 317 people and injured 109 on May 6, 1840, along the Mississippi River in Louisiana and Mississippi. The official death toll may not have included slaves, according to the Federal Emergency Management Agency.

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Photos:Photos: 10 deadliest U.S. tornadoes

10 deadliest U.S. tornadoes – 3. The "St. Louis Tornado" killed 255 people and injured 1,000 on May 27, 1896, in Missouri and Illinois. It had winds of between 207 mph and 260 mph.

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Photos:Photos: 10 deadliest U.S. tornadoes

10 deadliest U.S. tornadoes – 4. The "Tupelo Tornado" killed 216 people and injured 700 on April 5, 1936, in the northeastern Mississippi city.

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Photos:Photos: 10 deadliest U.S. tornadoes

10 deadliest U.S. tornadoes – 5. The "Gainesville Tornado" was a pair of storms that converged April 6, 1936, in Gainesville, Georgia, killing 203 people and injuring 1,600. The tornado destroyed four blocks and 750 houses in the northern Georgia town.

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Photos:Photos: 10 deadliest U.S. tornadoes

10 deadliest U.S. tornadoes – 6. The "Woodward Tornado" wreaked havoc across parts of Texas, Oklahoma and Kansas on April 9, 1947 killing 181 people and injuring 970. The funnel cloud reportedly was more than a mile wide in places.

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10 deadliest U.S. tornadoes – 7. The tornado that struck Joplin, Missouri, on May 22, 2011, killed 158 people and injured more than 1,000. The storm packed winds in excess of 200 mph and was on the ground for more than 22 miles.

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Photos:Photos: 10 deadliest U.S. tornadoes

10 deadliest U.S. tornadoes – 8. The "Amite/Pine/Purvis Tornado" killed 143 people and injured 770 on April 24, 1908. The storm left only seven houses intact in Purvis, Mississippi, and also caused damage in Amite, Louisiana.

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10 deadliest U.S. tornadoes – 9. The "New Richmond Tornado" killed 117 people and injured 200 on June 12, 1899, in New Richmond, Wisconsin.

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Photos:Photos: 10 deadliest U.S. tornadoes

10 deadliest U.S. tornadoes – 10. The "Flint Tornado" killed 115 people and injured 844 on June 8, 1953, in Flint, Michigan. The tornado was the deadliest twister ever recorded in the state.

A tornado's shearing, twisting winds can exceed 300 mph, and though they usually last only seconds, some cyclones endure much longer, razing swaths up to a mile wide that scar landscapes for months to come and inflict tragic human losses.

Though meteorologists have not finished analyzing the most recent Arkansas storm, so far the state has been spared an EF5, the NWS says.

CNN meteorologist Chad Myers estimates that the winds that ravaged the town of Mayflower, Arkansas, on Sunday had speeds of 130 to 150 mph, which would correspond to an EF3 tornado, which the Fujita Scale describes as "severe."

Let's take a look at the nature of the strongest tornadoes, the EF5s, the strongest storms on Earth.

Where do storms of this strength most commonly hit?

While EF5 storms are rare, the area in the Great Plains known as "Tornado Alley" gets more than its share. The alley runs through Texas, Oklahoma, Kansas and Iowa. There also seems to be a focus for strong tornadoes in an area known as "Dixie Alley," which covers parts of the Southeast and includes Mississippi, Tennessee, Alabama and Georgia.

What factors give rise to a storm of this strength?

A number of factors have to come together at the right time and place to produce a strong tornado. The clash of warm and cold air at the surface combined with lift in the atmosphere and strong winds, both at the ground and high above, help contribute. The greater the temperature differences and the winds, the greater the chance for supercells, the thunderstorms that produce tornadoes.

How long does it take to assess the strength of a storm? Why does it take so long?

After a tornado, the local National Weather Service office sends a team to take a look at the damage. In the case of the monster twister in Moore last year, the Norman, Oklahoma, office sent numerous teams into the field to evaluate damage. Since this storm path was 17 miles long and the damage path was so wide, it took time to see all of the damage.

The strongest tornado on record to date struck Moore in 1999. It had winds recorded at 318 mph at 300 feet above the Earth's surface. Officials estimated winds at the surface were at 250 mph.